Because of their size and horns, rhinoceroses don't have many enemies'except human beings. At one time, about one hundred species of rhino roamed the earth. Today only five species remain, and they too are in great danger. Illegal hunters continue to kill rhinos for their valuable horns, which become an ingredient in traditional medicines or are carved into decorative shapes. But groups around the world are fighting to stop the extinction of these unique creatures. Learn more in this edition of Nature Watch.Walker, Sally M. is the author of 'Rhinos ', published 2006 under ISBN 9780822566007 and ISBN 0822566001.